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Dear Liu,<br>
<br>
It is related to the Kramers-Krönig relation. <br>
Looking at these equations you will see that eps2 is an additive
quantity, while for eps1 you should consider (eps1 - 1) ... <br>
<br>
Regards<br>
<br>
Xavier<br>
<br>
<br>
<br>
On 06/30/2011 07:47 PM, gbliu wrote:
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Dear all,<br>
<br>
I calculated the dielectric function of fcc Au, using a k-mesh
15x15x15. After the scf run, my step is as follow:<br>
1. x opitc<br>
2. Calculate intraband contribution, by setting swith 6 in
fccAu.injoint file. Then I run "x joint". <br>
3. Read the file fccAu.outputjoint, and get the plasma
frequencies: 9.0075eV for both xx and zz.<br>
4. Save a copy of fccAu.joint as <b>Intra.epsilon</b>, in which
is the data of dielectric function from intraband contribution
(Drude model).<br>
5. Change the swith in fccAu.injoint from 6 to 4. "x joint" to
compute epsilon.<br>
6. "add intraband" set to 0 in fccAu.inkram, then "x kram", save
the file fccAu.epsilon as <b>noIntra.epsilon</b><br>
7. "add intraband" set to 1 in fccAu.inkram, then "x kram" again,
save the file fccAu.epsilon as <b>withIntra.epsilon</b>.<br>
8. Then I compare the data in files Intra.epsilon, noIntra.epsilon
and withIntra.epsilon, I found that:<br>
Im(withIntra.epsilon) = Im(noIntra.epsilon) + Im(Intra.epsilon)<br>
But Re(withIntra.epsilon) = Re(noIntra.epsilon) +
Re(Intra.epsilon) - 1<br>
<br>
So I'm confused why not "Re(withIntra.epsilon) =
Re(noIntra.epsilon) + Re(Intra.epsilon)" ?<br>
How does the difference "1" come from?<br>
<br>
Can anyone help me ?<br>
<br>
Thanks in advance.<br>
<br>
---------fccAu.inop-------<br>
99999 1 number of k-points, first k-point <br>
-5.0 3.0 9999 Emin, Emax for matrix elements, NBvalMAX<br>
2 number of choices (columns in *outmat): 2: hex or
tetrag. case<br>
1 Re xx<br>
3 Re zz<br>
OFF ON/OFF writes MME to unit 4<br>
--------------------------<br>
<br>
-------fccAu.injoint------<br>
1 9999 9999 : LOWER,UPPER and (optional)
UPPER-VAL BANDINDEX<br>
0.0000 0.00100 1.0000 : EMIN DE EMAX FOR ENERGYGRID IN ryd
<br>
eV : output units eV / ryd / cm-1<br>
<b> 4 </b> <b>"first I use 6, then 4" </b>
: SWITCH <br>
2 : NUMBER OF COLUMNS<br>
0.1 0.1 : BROADENING (FOR DRUDE MODEL - switch
6,7 - ONLY)<br>
--------------------------<br>
<br>
-------fccAu.inkram---------<br>
0.1 Gamma: broadening of interband spectrum<br>
0.0 energy shift (scissors operator)<br>
<b>1 "first I use 0, then 1" </b> add intraband
contributions? yes/no: 1/0<br>
9.0075 9.0075 plasma frequencies (from joint, opt 6)<br>
0.10 0.10 Gammas for Drude terms <br>
------------------------------<br>
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Best regards!
Liu Guibin
Postdoctoral Fellow,
Department of Physics,
The University of Hong Kong
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